IN TF RNATIONAI
ADVANTAGES OF REFRACTORY CONCRETE
Heat Resistant Concrete
CONDUCTIVITY — Charts
CURING 10 > 16
DRYING BEFORE USING
FLOORS — Heat Resistant
FLUES AND DUCTS
FOUNDATIONS — Heat Resistant
HEAT RESISTANT CONCRETE
HIGH TEMPERATURE FURNACES (2750° F. and Over)
LOW TEMPERATURE FURNACES (2000° F. and Under)
MEDIUM TEMPERATURE FURNACES (2000° F.— 2750° F.)
REFRACTORY CONCRETE — General
SEALING OVENS, KILNS AND FURNACES
STACKS AND CHIMNEYS
>|iyrlght i!>4o. . x f i : • — Lnmnlte Cement ( o
1 1 1 1 • -« 1 In I > A
The Atlas TuMNITE. Cement Go.
United States Steel
Chrysler Building, New York • 208 South La Salle Street, Chicago
Refractory Concrete is a concrete having refractory properties and
suitable for service at high temperatures in furnaces and other in-
dustrial heating units. Refractory Concrete has cold strength, as
placed, similar to that of ordinary structural concrete. After ex-
posure to service temperatures a fired strength or "ceramic bond"
is built up by the vitrification of the constituent materials.
Made with LUMNITE, refractory aggregates and water, Refractory
Concrete is mixed and placed by methods similar to those employed
for structural concrete. Furnace walls or other sections may be cast
in place using forms of wood or steel. Precast units may be made
and put in service as required without pre-firing. See Pages 6 to 13.
Economy of installation, maintenance and operation is the primarx
reason for the rapid extension of the use of Refractory Concrete.
Materials are readily available. LUMNITE is sold by building
supply dealers throughout the United States and Canada. Reserve
stocks are maintained by the Atlas Lumnite Cement Company at
twelve points in the United States. Aggregate, such as fire brick
grog, can be prepared from salvaged refractories or may be pur-
chased from manufacturers of refractories. Stocks of LUMNI1 I
and aggregates in the plant represent but a small inventory item.
The adaptability of Refractory Concrete makes possible the ready
placing of monolithic walls, linings and arches in locations which
P.M. I -
Refractory Concrete Arch in
This pre-cast arch, 15 feet 8 inches
overall length, was hoisted into
place 24 hours after casting.
would otherwise require the use of special shapes and entail high
erection costs. Maintenance is facilitated by a cast-in-place refrac-
tory or by unfired precast units made to nt the job. The high 24-
hour strength of LUMNITE concrete makes possible the applica-
tion of the Kill working load within a day of placing, lor the same
reason precast units may be handled and installed within 24 hours.
Opel Iting economy results from the installation of monolithic Re-
fractory ( oncrete walls — walls without joints. Combinations of
refractory .\nd insulating sections can be worked out with regard
only to the desired thermal effects. The designer is not restricted
by standard sizes of units and conventional wall thicknesses.
Doors for Core and Mold Drying
Ovens in a Steel Foundry.
Pag i 3
Refractory Concrete Roof Slab for
Pit Annealing Furnace.
This roof slab had been in service
about two years when the picture
LUMNITE concrete exposed to temperatures which cause the dis-
integration of ordinary concrete is known as Heat Resistant Con-
crete when the temperatures are not high enough to vitrify the
material and form a ceramic bond. Furnace foundations, ducts
carrying hot gases and floors subject to soaking heat are typical
examples of Heat Resistant Concrete. Where ordinary structural
concrete either cannot be used or does not have an economic life,
concrete made with LUMNITE and suitable aggregates combines
structural strength and resistance to heat. See Page 14.
Insulating Concrete is essentially Heat Resistant Concrete with low
thermal conductivity. Several special aggregates are commercially
available for making light-weight concrete with excellent insulating
properties. The type of aggregate selected depends on the thermal
conductivity and heat storage capacity desired in the Insulating
Concrete. LUMNITE is used as the binder for the special aggregates
because the concrete must be stable under high temperatures.
Insulating and refractory characteristics may be obtained together
through the use of such aggregates as refractory-insulating-fire-
brick grog or other special materials. See Page 19.
These three types of concrete — Refractory, Heat Resistant, Insul-
ating — provide for a wide range of thermal conditions. All are made
with LUMNITE and aggregates selected according to the require-
ments of the particular installation. With LUMNITE in stock and
a supply of low-cosc aggregates, materials are available for a great
variety of furnace construction and maintenance jobs.
Refractory Concrete Car Top
and Baffles for Car Type
This furnace also has precast Re-
fractory Concrete roof arch sec-
tions with span of about 14 feet
LUMNITE when mixed with water sets and hardens by chemical
action without the application of heat. It is used 03 the binder tor
refractory, heat resistant and insulating aggregates in the making
of these several kinds of concrete.
Coiicretl made with LUMNI'I'l. ind suitable a^re^tes has the
property ot retaining i considerable part of its cold strength ifter
contimi I exposure at high temperatures. l.UMNITl is not m it-
h refractory material. It is used in making Refractor) Con-
rel I" tUSC its efleCtiveneSI as a binder is not destroxed by the
serv ice temperal in es.
I I'MNIII Is not a Portland cement ami it diHcrs from Portland
cerium in chemical composition and physical properties. LUMNI I I
is .1 IK mm
aluminate cement .is distinguished rrom portland in
which the principal constituent! are calcium sili itcs. I he calcium
luminatc cementa arc the only commercial hydraulic cementi m men
have heat resistant properties required fof Ketractorv < micretc.
I UMNTl I is the only caicium alumm..u cment m.iJc in America.
LUMNI I"! ( onu-tte Used to Insulate
Floor Slab .ind Burner Ports of
Oil Still Furnace.
LLMNITt slab is placed over ordi-
nary concrete foundation. Note ven-
tilating ducts through floor slab.
The proportioning of mixes and grading of aggregates for Refrac-
tory Concrete differ in principle and practice from those employed
for structural concrete. The manipulation of LUMNITE also dif-
fers from that of ordinary structural cements. On the following
pages we give suggestions for making Refractory Concrete suitable
for several kinds of service. Great diversity in operating conditions
and service requirements makes it difficult, if not impossible, to lay
down hard and fast rules for formulating mixes. In general, the
suggestions are based on satisfactory installations made by users of
LUMNITE may be used as a binder with acid, basic or neutral re-
fractory aggregates. The refractory properties of the concrete de-
pend on the aggregate. These properties are not necessarily the same
as those of the aggregate in its original state. In general, the insu-
lating value of Refractory Concrete will be somewhat greater than
that of the refractory material with which the concrete is made.
The refractory limit will be slightly lower than that of the aggre-
gate. Refractory Concrete has consistently shown excellent non-
spalling characteristics in tests and in service.
Selection of aggregate depends on service conditions and availability.
On Pages 12 and 13 those which may be used within certain tem-
perature ranges are listed under the classifications:
2000° F. and under
Low Temperature Furnaces
Medium Temperature Furnaces
High Temperature Furnaces 2750° F. and over
Particle size and grading of aggregate are of the greatest importance.
Regardless of type, the aggregate should range from the maximum
size particles through all intermediate sizes down to and including
fines and dust. Maximum size may be %" to 1 J4" depending on
thickness of section. When large sizes are not available aggregate
of smaller maximum size may be used.
Approximately 5 0% of total aggregate should pass a /g" screen.
IS', to 18% should pass a 100 mesh screen. If necessary add fines
to original crushing. Uniform grading is required in any case, i.e.,
there must be intermediate sizes between the fine and the coarse
When accurate sizing is impracticable an ordinary lly screen may
be used. 3 5% of the total aggregate should pass the fly screen. Uni-
formity of grading can be determined visually by the presence of
all particle sizes between fines and coarse.
(arc should be taken to avoid mixing the clay fire brick with other
kinds of bricks, such as common or silica brick. Old mortar and
cements adhering to the brick should be cleaned off to prevent con-
tamination of the LUMNTTE.
Service temperature determines proportions of mix. Proportions
for the several temperature ranges arc given on Pages 12 and 13.
Slow Cooling Pit for Steel Billets.
LUMNITE Refractory Concrete
used for walls and bottom. Arched
cover lined with LUMNITE Insu-
lating Refractory Concrete to re-
duce weight and heat loss.
Accurate measurement of binder and aggregate is important. One
be weighed. For example— if one cubic foot of Refractory Concrete
6 r one Font
is desired, using a 1:4 mix, measure
cubic foot box, weigh out 23 ^ pounds of LUMNITE. Weigh the
LUMNITE, do not measure in the cubic foot box. A finely divided
material, such as LUMNITE, cannot be accurately measured by
volume. It should be weighed when a fraction of a bag is needed.
All proportions are stated in terms of total aggregate. When two
or more sizes are used to obtain proper gradation, proportions given
in this book refer to quantities of aggregate after mixing together
the two or more sizes.
I or most types of installations forms similar to those employed in
concrete construction arc used. Many fire doors because of their
shape do not need any side molds or forms. When it is desired to
have the lining thicker than the side flanges of the door, wooden
forms or molds can be made to give the desired thickness ot the
lining. It is sn jested that such forms be made with Ul inside taper
and greased so they can be easily removed. If tapered sides are
Gis Gun Blocks for Coke Ovens
An\ special shape may be made at
the plant required. Refractory
properties are the same as cast-
m-place Refractory Concrete.
Precast Refractory Concrete Shapes
The rapid hardening of LUMNITE
facilitates the casting of special
hapes. They may be 1> idled and
installed the day after making.
objectionable the corners of the wooden
form may be fastened with screws or
bolts for easy removal.
Metal reinforcement cannot be used in
Refractory Concrete in the same man-
ner as in ordinary structural concrete.
At high temperatures carbon steel loses
strength and disrupts the concrete.
Heat-resistant steels have given better
results. Special methods of design are
required when Refractory Concrete is
to be used for structural purposes. In-
formation on this subject may be ob-
tained from the Atlas Lumnite Cement
Company, 13 5 East 42nd Street, New
York, N. Y.
When mixing Refractory Concrete
first moisten the aggregate until it will
not readily absorb any more water,
then add the LUMNITE and mix to a
Concrete Coke Oven Door
This photograph was taken
after the lining had been
in continuous service for
more than 5 years.
Add sufficient cold water, not over 80° F., to make the mixture
plastic, soft and sticky. If the aggregate contains sufficient fines
and dust the mix will be plastic, easily placed by spading without
ramming, and will not release free water. If the aggregate contains
insufficient fines and dust to produce this consistency, the addition
of small percentages of plastic fire clay will increase the plasticity.
Fire brick aggregates will require a longer period of mixing than
ordinary concrete aggregates in order to permit complete absorp-
tion of the water. Should the mix become dry during placing add
more water and remix.
example, if a door is being lined which requires three batches, place
the next batch for the second third of the area for the complete
depth; the next batch to cover the last third of the area for the
complete depth. The concrete should be spaded to densify and con-
solidate it. If a smooth surface is desired use only a wood float. A
cement gun is sometimes used for placing refractory mortars.
Best results are obta.ned if the exposed surface of the concrete b
kept moist by sprinkling from six hours after mixing until twenty
hours after mixing. This is of particular importance when dense
aggregates are used, or the work is done in a place where high atmos-
pheric temperatures prevail or where the air is very dry.
The rapid hardening of 1 UMNITE greatl) aids the drying of Re-
fractor) < terete linings. Predrying is important in work of con-
iiderabk man. If the concrete is to be subjected to high tempera-
Front Arches in Forge
An example of Re-
fractory Concrete m
set I ice. The um <>1
precast units facili-
tates replacement and
Aggregate and mol
used in making th
precast arch section
shown m the abov
picture. From left t
right, grog pile, arc
section on end, she*
steel mold, end vie^
of arch section.
REFRACTORY CONCRETE TOPS FOR TUNNEL KILN CARS
The group of cars in the picture is part of the equipment of 50 cars, all topped
with Refractory Concrete, in use at one tile plant.
tures suddenly, as in the case of many door linings, better results
will be secured if 48 to 60 hours elapse before the lining is put into
service. When it is desirable to use the linings before this period a
small amount of artificial drying may be necessary. The same care
when first heating Refractory Concrete is required as when using
When Refractory Concrete is heated on all sides, there is a noticeable
shrinkage which is offset to a considerable extent (not entirely) by
a small thermal expansion. When heated only on one side, shrinkage
may develop hair cracks on the hot face or a few cracks extending
into the concrete.
In each case, the thermal expansion of the materials while hot prac-
tically compensates for the initial shrinkage. In lining a furnace
door, for example, the frame is filled with concrete. No allowance
is made for expansion of the concrete.
Page 1 1
Proportioning and Materials for Low
Low Temperature Service 2000° F. and Under
( 1 bag LUMNITE to 4 cu. ft. of aggregate) .
Note— 1 bag LUMNITE=1 cu. it. =94 lbs.
See "Proportioning," Page 8.
A one bag batch of 1:4 mix will yield ap-
proximately four cubic feet of Refractory
The load-bearing capacity of Refractory
Concrete in service at 2000° F. and under
will be increased with a somewhat richer
mix. A 1 : 3 mix should be used where heavy
loads will be imposed directly on the Re-
fractory Concrete. This condition holds for
some ceramic kiln car tops and some anneal-
ing furnace car tops wnere heavy ware and
Fire Clay Grog
Firebrick Grog (RIFB)
Crushed Insulating Brick
Crushed Pottery Saggers
Light Weight Refractory
Diatomaceous Silicaf (Service
Maximum 1800° F.)
When both insulating and refractory prop-
erties are desired vermiculite may be used
in combination with the fireclay and LWR
aggregates. The addition of vermiculite in-
creases the insulating value but decreases the
strength and resistance to abrasion.
:: Such as Gravelite, Haydite, Raylite
tSuch as Sil-o-cel C-3
ANNEALING FURNACE CAR TOP
A Refractory Concrete top 40 feet long, 12 feet wide, cast in place.
Page 1 2
Medium Temperature Service 2000° F. to 2750° F
2000 F.-2250 F.
2250 F.-2500 F.
Bags Cubic Feet
Certain installations may require the aggre-
gates suggested for high temperature fur-
When aggregates recommended for high
temperature furnaces are used for medium
temperature furnaces a 1:6 mix should be
Fire Clay Grog
Refractory Insulating Firebrick Grog
Crushed Pottery Saggers
For service between 2500° F. and 2750 I
IggregatC should ha\e | softening point oi
Cone 30 or higher.
""Maximum service temperature t<>r am
Rll'h grog should be obtained h<>m the
High Temperature Service 2750° F. and Over
1 bag LUMNITE to 6 or 7 cu. h. of aggre-
When Olivine is used in high tempcratur
service it is desirable, and in mo t asea tu »-
sary, to remove the material passing a %"
screen and substitute tines oi one 01 the
ills, preferablv chromite. A mix
of 1 bag of LUMNITE, 4 cubic teet chro-
mite or fused alumina, graded from \ to
dust, and 4 cubic feet of Olivine, graded
tnini I /4 " to %" or ! W% ls suggested
I used Alumina
SUMMARY OF REFRACTORY CONCRETE Ml XI s
Up to 2000 F.
2000 F. to 2250 F.
2250 F. to 2500° F.
2500° F. to 2750 F.
Above 2750 F.
KINO OF AGC.KH.ATr.
6 to 7
Clay aggregates; olivine
Clay aggregates; olivine
Clay aggregates; olivine;
Clay aggregates; olivine;
*Sce list under "High Temperature Service"
per cu. yd
The disintegration of ordinary concrete by continued exposure to
high temperatures creates a serious problem in the construction of
furnace foundations. Floors under and around furnaces, ducts and
flues carrying hot gases are subject to the same destructive effect.
Experience has shown that LUMNITE concrete when made with
suitable aggregates offers a much greater degree of resistance to the
disintegrating effect of "soaking heat." Although the strength of
all concrete is lowered by continuous exposure to heat, many of the
advantages of concrete construction are retained in LUMNITE
Heat Resistant Concrete.
For Heat Resistant Concrete, materials which release lime must not
be used. LUMNITE is the only American-made hydraulic cement
which does not release lime during the hardening period or after
the concrete has been exposed to heat.
Heat Resistant Foundations
Proper design of the foundation will facilitate its construction with
LUMNITE concrete and extend its service life. In all cases the
foundation should be so constructed as to dissipate the heat which
is built up in the mass of concrete exposed to the high temperatures.
Ventilating ducts through the concrete will assist such dissipation.
This ventilation also aids in carrying off the heat generated by the
hydration of the LUMNITE. The hardening action of LUMNITE,
on account of its rapidity, causes the evolution of considerable heat
during the first 24 hours after the concrete is mixed.
Heat Resistant and Insulating Concrete, in combination, are some-
times used in furnace construction. An insulating slab, similar to
that shown in the picture at the bottom of Page 5 is placed on a heat
resistant foundation. Heat Resistant Concrete is employed when
it is expected that relatively high temperatures will eventually be
built up in the foundation during continuous operation of the
Page 1 4
HEAT RESISTANT CONCRETE
Construction view of LUMNITE
concrete slab to support regenera-
tor walls of underburner regenera-
tive by-product coke ovens.
Old fire brick, paving brick or hard-burned common brick, when
crushed to the required sizes, will be found more satisfactory than
sand and gravel which are often high in silica. Trap rock, both fines
and coarse, may be used.
Light-weight refractory aggregates, such as Gravelite, Haydite and
Raylite, are suitable especially where insulation is desired. Air-cooled
blast furnace slag has been used at temperatures below 1000° F.
Slag is not recommended above that temperature.
Lime-releasing aggregates should be avoided. Materials such as silica
aggregates which undergo sudden volume change when heated must
not be used.
The coarse aggregate should be retained on a screen having round
openings of l / 4 ". The maximum size particle may be from %" to
1 y 2 ". The fine aggregate should pass a l / 4 " round opening and have
some fines passing a 100 mesh sieve.
1 bag (1 cu. ft.) of LUMNITE, 2j/ 2 cu. ft. fine aggregate, and
iy 2 cu. ft. of coarse aggregate. If the mix is harsh, increase the fine
aggregate and decrease the coarse aggregate in equal proportions.
ticity must not be used with LUMITE.
LUMNITE concrete is placed in the same manner as ordinary con-
crete. When large masses of LUMNITE concrete are desired it may
be advisable to place them in more than one operation. In general
the thickness of a large slab placed at one time should not be greater
than 1 5 inches, unless special provision is made for curing. When a
large mass of concrete is placed in two layers 24 hours should be
allowed for the curing of the first layers before the concrete for
the second layer is placed.
Page 1 5
Pag i 16
After the concrete has set (from 6 to 10 hours after placing, de-
pending on atmospheric conditions and temperature of concrete
when placed) the concrete should be kept moist by sprinkling with
water until it is 24 hours old. The time for first application of
curing water may be determined by rubbing the surface with a
moistened finger. If the finger is clean after the rubbing, sprinkling
should start. If the finger is soiled by the test, sprinkling should be
Floors Exposed to Direct or Indirect Heat
For best results a monolithic, one course heat resistant floor should
be placed. Thin heat resistant top courses on ordinary concrete base
slabs are not recommended.
Floors continuously exposed to high temperatures do not have the
wearing quality of ordinary, unheated concrete. They cannot be
expected to withstand abrasion from trucking, dragging of skids or
other severe wear.
Crushed old firebrick, paving brick or hard-burned common brick
may be used. Trap rock, fine and coarse, is also satisfactory. The
harder aggregates will give a better wearing surface. Light weight
refractory aggregates are serviceable from standpoint of heat resis-
tance but should not be used for floors subject to traffic.
A mix of 1 bag LUMNITE, 2 l / 2 cu. ft. fine aggregate, 2 l / 2 cu. ft.
coarse aggregate is generally satisfactory. The mix may be adjusted
as described under "Heat Resistant Foundations" to improve work-
ability for placing and finishing.
All operations in placing LUMNITE Heat Resistant Floors, except
as noted above, are the same as for LUMNITE concrete floors for
the usual structural purposes. Full information on this subject will
be found in the pamphlet "LUMNITE for Structural Concrete."
Heat Resistant Con-
crete Foundation for
A slab approximately
six inches thick was
placed over ordinary
Billet Heating Furnace erected on
LUMNITE Heat Resistant Con-
crete slab. The three furnace doors
are lined with Refractory Concrete
Flues and Ducts
LUMNITE Heat Resistant Concrete is an adaptable material for
the construction of ducts carrying hot gases. Many satisfactory in-
stallations have been made, especially in oil refineries.
Several types of duct have been developed by LUMNITE users.
Monolithic LUMNITE concrete structures have been built in some
cases. In others precast sections are used. LUMNITE protective
linings have been placed in ducts built of reinforced portland ce-
ment concrete. Where ducts are placed partially underground or
where dissipation of heat is inadequate, it is desirable to provide
ventilating flues in the concrete. One convenient method is to con-
nect the ventilating flues into the chimney. The draft will provide
a continuous flow of air to carry off the heat and reduce the heat
storage in the concrete.
The light-weight clay aggregates are in general use for these
LUMNITE concrete ducts. The concrete has adequate structural
strength, low heat storage capacity and high insulating value. (See
information on Insulating Concrete on following pages.)
LUMNITE is not a portland cement. Methods of use are somewhat
different from portland cement practice, especially in curing pro-
cedure. The pamphlet "LUMNITE for Structural Concrete" should
be studied carefully before constructing foundations or floors of
Heat Resistant Concrete.
Sealing Ovens, Kilns, and Furnaces
Prevention of infiltration of air in ovens, kilns and furnaces is of
prime importance in many industr.es. When the equipment .s ex-
posed to the elements it must be sealed against the entrance of water
,s well as air. LUMNITE mixtures have been used for sealing such
units with satisfactory results, both on sheltered equ.pment and on
that exposed to wind and rain.
The mixes used approximate one part LUMNITE to 2J4 parts
aggregate graded from / 8 " or 3/16" maximum size, down to and
including fine particles. For application with a trowel sufficient
water should be added to give a plastic mix. For cement gun work
the amount of mixing water will be controlled by the operation of
The aggregate used with LUMNITE should be of the same general
the brick to which the mortar is applied. For example, on
clay fire brick, ground clay fire brick or Haydite can be used as
the aggregate. On silica brick, silica sand should be used.
The wall should be cleaned of all dirt and loose particles. When the
temperature of the surface of the wall to which the mortar is to
be applied is 200 ° F. or lower, the brick wall should be moistened
before the mortar is applied. At temperatures above 200° F. it is
doubtful if the wall can be successfully moistened.
Particularly on vertical or hot walls the use of a cement gun for
applying the mortar will be of great help in obtaining the best re-
sults^ When no cement gun is available the mortar may be applied
by troweling. The seal coat is usually from l / 2 " to %" thick.
Sprinkling of the LUM?
Under ordinary conditions at atmospheric temperatures the set will
occur in 6 to 8 hours after placing. When the mortar is applied to
hot walls the set will be speeded up. The test and directions
for curing on Page 16 should be followed.
Stacks and Chimneys
LUMNITE is widely used for protective linings of steel stacks and
for mortar in brick and tile chimneys. In addition to refractory
properties LUMNITE mortar is resistant to the corrosive action of
A special illustrated folder, "LUMNITE in Stacks and Chimneys,"
describes these uses.
A Typical Industrial Stack with
LUMNITE Refractory, Insulating,
Corrosion Resistant Lining. Same
type of lining used in boiler
Pagk 1 8
Insulating Concrete is a special type of Heat Resistant Concrete. It
may also have refractory properties, in which case it is essentially
Refractory Concrete of low thermal conductivity. Insulating Con-
crete made with certain aggregates has structural strength greater
than that of most walls laid up with the usual insulating brick.
Structural strength and low thermal conductivity make possible the
use of Insulating Concrete as a back-up to Refractory Concrete or
other refractories. The Insulating Concrete gives added strength
to the wall. It can be used in many cases to replace both insulating
brick and the outer layer of common brick. Higher insulating value,
lower heat storage, ample strength, reduced dead load and lower
initial cost result from the use of Insulating Concrete in this manner.
Steel jackets can often be eliminated when Insulating Concrete is
used for outside walls of furnaces. The walls may be reinforced
with angles or T-irons. One flange is embedded in the concrete
and the other flange (or flanges of T-iron) is exposed to the air
on the outside of the wall. The embedded flange should not extend
more than halfway through the thickness of the Insulating Con-
crete. This reinforcing will greatly increase the structural strength
of the outside walls, eliminating the more expensive method of
jacketing the furnace with steel sheets or plates.
Furnace walls of Insulating Concrete may be built without a fire
brick inner lining when the concrete is made with suitable aggre-
gates. Monolithic walls with few or no joints are more efficient in
operation than brick masonry walls with many joints. A surface
wash or coating on the inside of the furnace is seldom necessary
when the higher-strength, light-weight, clay aggregates are used.
Refractory-Insulating Concrete is made, with LUMNITE, at about
the same cost as ordinary Refractory Concrete. A monolithic Re-
fractory-Insulating Concrete wall or roof arch can usually be built
at a cost comparable with plain refractory construction.
Page 1 9
Annealing Furnace Cover lined
with Refractory Concrete. A
feet in diameter.
The aggregate for Insulating Concrete should be as strong struc-
turally as possible without sacrifice of the required insulating value.
Strong structural concrete cannot be made with structurally weak
obtained through the use of the more efficient, but structurally
weaker, insulating aggregates. Combinations of aggregates can be
used to produce concrete having the highest insulating value con-
sistent with the structural strength required for any particular in-
Aggregates commonly used for Insulating Concrete at temperatures
up to 2000° F. include: Gravelite, Haydite, Raylite, Sil-o-cel, ver-
miculite, The first three are light-weight processed aggregates of
relatively high strength. Sil-o-cel is one of a number of diatomaceous
aggregates of medium strength.
Vermiculite is an exfoliated mica of low strength marketed under
various trade names, one of which is Zonolite. With vermiculite mixes
the concrete should be compacted after placing to secure greater
strength. Degree of compaction depends on proportion of vermicu-
lite used. Conductivities of several mixes of vermiculite with other
insulating aggregates are given in the table on Page 21. It is also used
in combination with crushed firebrick.
In temperatures above 2000 F. several light-weight aggregates made
from fire clay are available. (These are generally known as insu-
lating fire brick grogs. ) The names of manufacturers and producers
of these special aggregates can be obtained from The Atlas Lummte
LUMNITE Heat Resistant — Insulating Concrete is used
extensively in Oil Refinery Construction.
LUMNITE concrete made with a light-weight clay aggre-
gate is used for insulating tube sheets, tube header com-
partments and air-cooled floor slab in the Oil Still Furnace
pictured in the foreground.
LUMNITE concrete slabs are also placed at the top of
heaters of this type to act as insulation and provide an
upper working floor.
Proportions of LUMNITE and one or more aggregates vary over a
wide range. They depend on the required insulating value (thermal
conductivity) and on the desired structural strength. Mixes such
as those tabulated below are in common use.
H \C M
B.T.U./sq. ft./in./°F. hr
4 Light wt. clay Agg.
5 Light wt. clay Agg.
6 Light wt. clay Agg.
Light wt. clay Agg*
3 Light wt. clay Agg
2 Light wt. clay Agg
Approximate values at 1500 F. Mean Temperature
The mixes are tabulated in the order of structural strength, the
strongest (1:4 with clay aggregate) at the top, the weakest (1:6
with vermiculite) at the bottom.
Details of mixing, placing and curing Insulating Concrete are the
same as for Refractory Concrete, see Pages 9 to 11.
Page 2 I
Bulkhead of Open Hearth Furnace.
LUMNITE Insulating Concrete ap-
plied with a cement gun. Note
sheet metal supports inserted at
every fourth joint.
Insulation applied to a cold furnace frequently is cracked
by expansion when the furnace is heated. Infiltration of
air through the cracks reduces the efficiency of the furnace
and increases operating costs. Application of an insulating overcoat
to the hot furnace prevents this infiltration to a large extent.
LUMNITE insulating mixes applied with a cement gun solve the
problem of placing insulation on a hot furnace.
The application can be made while the furnace is in operation. The
refractory insulating materials are expanded by the heat of the
furnace when the mixture is applied. Cooling of the furnace further
compresses the insulation , which s hould have sufficient resilience to
minimize cracking. The insulation may be built up to any desired
thickness by shooting on successive coats.
Any of the aggregates suggested for Insulating Concrete may be
used with LUMNITE for application with a cement gun. Aggre-
gate should be selected in accordance with the temperature condi-
tions, size and grading being determined by the requirements of
cement gun work.
Suitable proportions have been worked out in the field by a number
>f users of these LUMNITE mixtures for their special purposes.
Proportions will vary with aggregates used and working conditions.
Mixtures as lean as 1 bag of LUMNITE to 10 cubic feet of aggre-
gate have been applied successfully. If greater strength is needed
the mix may be as rich as 1 bag of LUMNITE to 5 cubic feet of
aggregate. With the leaner mixtures it may be necessary to add a
small amount of fireclay to provide necessary adhesiveness and pre-
vent excessive rebound.
ME A N TEMPERA TUR>
RIFB— REFRACTORY INSULATING FIREBRICK
LWR — TYPICAL LIGHT WEIGHT REFRACTORY
CONDUC Tl VI TY CHART
Conductivity Chart No. 2
The curves were prepared from data
obtained from a number of manufac-
turers and other sources. The several
aggregates are believed to be typical of
those in their respective classes*
Conductivity Chart No. 1
These Conductivity Charts show com-
parative insulating values of several
types of Refractory Concrete and other
MEAN TEMPERATURE V
CONDUCTIVITY CHART H
/ L OMNI ra ■ FINE 1 1lk)kE l
' CCAJSE O
L- = — — — — ' —
M 9 ^l ^^J^^^r M &
9 1 L
frp/r — kj
*- ' / ifet
4 /A Si h
?> V6 CRPS Hi
L INSULL 7
u bi m nr
Pace 2 i
4 O? / *y
73 /3. 3
7 09 3
**^ ^ .
E E I
Service ranges of several types of Refractory Concrete are indicated on the
left side of the chart. Service ranges for a number of Insulating Concretes
are shown on the right.
United States Steel